Fungal keratitis stands out as the predominant cause of blindness in patients with infectious corneal diseases in China [10][11]. Therapeutic keratoplasty plays a pivotal role in the management of progressive fungal keratitis when conventional pharmacological interventions prove ineffective. However, a significant contributor to the failure of corneal transplantation is the recurrence of postoperative fungal infections, with reported recurrence rates ranging from 5–14% [12][13][14]. Risk factors for infection recurrence encompass the size of corneal ulcer infiltration, graft dimensions, and the type of fungus involved [15][16]. Furthermore, comprehensive antifungal treatment prior to corneal transplantation constitutes a critical determinant for surgical success. In the presented case, the patient received standardized antifungal treatment post-diagnosis, resulting in favorable therapeutic outcomes. Undertaking corneal transplantation at this juncture successfully averted postoperative recurrence of fungal infections. Hence, judiciously selecting the timing for corneal transplantation emerges as a pivotal strategy in controlling the recurrence of fungal corneal ulcers.
Anterior chamber pus appeared on the 4th day after surgery. Based on past experience, we preliminarily suspected a recurrence of fungal infection and performed voriconazole anterior chamber lavage in the operative eye. However, the observed nature of the intraoperative pus appeared thin and lacked the characteristic viscosity seen in fungal infections [17][18]. Subsequent exacerbation of the patient's condition after antifungal treatment raised suspicions of potential infection by other pathogens. To rule out the possibility of corneal contamination from the donor, another patient who received a corneal transplant from the same donor tissue at the same time was continuously monitored and no signs of infection were found.
Due to the fact that microbial cultures and smear examinations of the affected cornea failed to detect any pathogens, we conducted next-generation sequencing (NGS) on the anterior chamber pus to identify the infectious agent. NGS is a diagnostic technique widely used in microbiological research but infrequently employed in routine clinical microbiological diagnostics. It offers a rapid and accurate advantage in determining the nature and type of infection in clinical diagnosis [19], particularly demonstrating excellent diagnostic value for infections on the ocular surface and within the eye [20]. When traditional microbiological tests in ophthalmology prove ineffective, it serves as an efficient auxiliary diagnostic tool, significantly improving the detection rate of microorganisms that are challenging to culture in clinical samples [21].
Ochrobactrum anthropi is widely present in the environment, soil, and water sources (physiological saline, preservative solutions, dialysis fluid) [5][22][23][24]. Additionally, Ochrobactrum anthropi has been isolated from human bodily fluids [25]. As a rare conditional pathogen, most reported cases involve hospital-acquired infections, with infected patients using various indwelling and invasive medical devices such as central venous catheters, artificial heart valves, and drainage tubes [6][26]-[27]. Existing clinical case reports have found that Ochrobactrum anthropi-induced endophthalmitis is more common after cataract intraocular lens implantation [8, 9][28], [29], [30], and there is also a reported case of infection after artificial corneal implantation [31]. Infections related to implants may be associated with the propensity of Ochrobactrum anthropi to adhere to the surfaces of synthetic materials [32]. Some studies also suggest a correlation between post-cataract surgery endophthalmitis and contamination of intraocular irrigation fluids [29]. Another report found that after thorough cleaning of the cannula kit of an ultrasonic emulsification machine, the hospital's outbreak of Ochrobactrum anthropi infection promptly disappeared [33]. This report further confirms this hypothesis.
Ochrobactrum anthropi, being an opportunistic pathogen, manifests infection significantly in individuals with compromised immune function and a history of both local and systemic antibiotic usage [8][34], [35], [36], [37]. However, in this particular case, the patient did not employ any indwelling or invasive medical devices, and comprehensive examinations, both physical and systemic, failed to reveal any symptoms. Based on the patient's medical history, the human Ochrobactrum anthropi infection in this case can be attributed to local immune function decline after corneal transplantation. In addition, the patient had a history of topical antibiotic use for 1 month prior to surgery, which increased the risk of human Ochrobactrum anthropi infection due to dysbiosis and antibiotic resistance.
Despite the generally perceived low virulence of Ochrobactrum anthropi, its infection rates have gradually increased in recent years due to its inherent multidrug resistance to antibiotics [38]. Ochrobactrum anthropi exhibits resistance to β-lactam drugs, particularly cephalosporins and penicillins, while being sensitive to quinolone drugs and aminoglycoside drugs, especially amikacin and gentamicin [39][40]. Our patient received prompt and adequate antibiotic treatment upon confirmation of the infection, effectively controlling the infection rapidly. However, it is noteworthy that, after 14 days of treatment, although the infection was well controlled, the corneal graft still exhibited cloudiness. Currently, while there have been numerous reports on endophthalmitis caused by Ochrobactrum anthropi, there is limited documentation on the toxicity of this bacterium to the cornea itself and the resulting pathological changes. Nandini et al. reported a case of corneal inflammation caused by Ochrobactrum anthropi infection, presenting as anterior chamber purulence in a patient with a history of viral keratitis. This case was ultimately diagnosed as Ochrobactrum anthropi infection, with corneal histopathological findings showing detachment of the posterior elastic layer [37]. Generally, bacterial infections can lead to pathological changes such as corneal opacification, edema, ulcer formation, and endothelial damage [41]. However, when infecting corneal tissues, Ochrobactrum anthropi, generally considered a Gram-negative bacterium with low virulence, may induce more severe pathological changes. The cloudiness of the corneal graft after Ochrobactrum anthropi infection in this case may also be related to the local eye drops and anterior chamber injections during the infection treatment, causing damage to the corneal endothelium [42][43][44].